[PATCH V11 01/17] asm-generic: ticket-lock: Reuse arch_spinlock_t of qspinlock

[Leonardo Brás]

On Sun, 2023-09-10 at 04:28 -0400, guoren at kernel.org wrote:
> From: Guo Ren <guoren at linux.alibaba.com>
> 
> The arch_spinlock_t of qspinlock has contained the atomic_t val, which
> satisfies the ticket-lock requirement. Thus, unify the arch_spinlock_t
> into qspinlock_types.h. This is the preparation for the next combo
> spinlock.
> 
> Signed-off-by: Guo Ren <guoren at kernel.org>
> Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> ---
>  include/asm-generic/spinlock.h       | 14 +++++++-------
>  include/asm-generic/spinlock_types.h | 12 ++----------
>  2 files changed, 9 insertions(+), 17 deletions(-)
> 
> diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h
> index 90803a826ba0..4773334ee638 100644
> --- a/include/asm-generic/spinlock.h
> +++ b/include/asm-generic/spinlock.h
> @@ -32,7 +32,7 @@
>  
>  static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
>  {
> -	u32 val = atomic_fetch_add(1<<16, lock);
> +	u32 val = atomic_fetch_add(1<<16, &lock->val);
>  	u16 ticket = val >> 16;
>  
>  	if (ticket == (u16)val)
> @@ -46,31 +46,31 @@ static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
>  	 * have no outstanding writes due to the atomic_fetch_add() the extra
>  	 * orderings are free.
>  	 */
> -	atomic_cond_read_acquire(lock, ticket == (u16)VAL);
> +	atomic_cond_read_acquire(&lock->val, ticket == (u16)VAL);
>  	smp_mb();
>  }
>  
>  static __always_inline bool arch_spin_trylock(arch_spinlock_t *lock)
>  {
> -	u32 old = atomic_read(lock);
> +	u32 old = atomic_read(&lock->val);
>  
>  	if ((old >> 16) != (old & 0xffff))
>  		return false;
>  
> -	return atomic_try_cmpxchg(lock, &old, old + (1<<16)); /* SC, for RCsc */
> +	return atomic_try_cmpxchg(&lock->val, &old, old + (1<<16)); /* SC, for RCsc */
>  }
>  
>  static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
>  {
>  	u16 *ptr = (u16 *)lock + IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
> -	u32 val = atomic_read(lock);
> +	u32 val = atomic_read(&lock->val);
>  
>  	smp_store_release(ptr, (u16)val + 1);
>  }
>  
>  static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
>  {
> -	u32 val = lock.counter;
> +	u32 val = lock.val.counter;
>  
>  	return ((val >> 16) == (val & 0xffff));
>  }

This one seems to be different in torvalds/master, but I suppose it's because of
the requirement patches I have not merged.

> @@ -84,7 +84,7 @@ static __always_inline int arch_spin_is_locked(arch_spinlock_t *lock)
>  
>  static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock)
>  {
> -	u32 val = atomic_read(lock);
> +	u32 val = atomic_read(&lock->val);
>  
>  	return (s16)((val >> 16) - (val & 0xffff)) > 1;
>  }
> diff --git a/include/asm-generic/spinlock_types.h b/include/asm-generic/spinlock_types.h
> index 8962bb730945..f534aa5de394 100644
> --- a/include/asm-generic/spinlock_types.h
> +++ b/include/asm-generic/spinlock_types.h
> @@ -3,15 +3,7 @@
>  #ifndef __ASM_GENERIC_SPINLOCK_TYPES_H
>  #define __ASM_GENERIC_SPINLOCK_TYPES_H
>  
> -#include <linux/types.h>
> -typedef atomic_t arch_spinlock_t;
> -
> -/*
> - * qrwlock_types depends on arch_spinlock_t, so we must typedef that before the
> - * include.
> - */
> -#include <asm/qrwlock_types.h>
> -
> -#define __ARCH_SPIN_LOCK_UNLOCKED	ATOMIC_INIT(0)
> +#include <asm-generic/qspinlock_types.h>
> +#include <asm-generic/qrwlock_types.h>
>  
>  #endif /* __ASM_GENERIC_SPINLOCK_TYPES_H */

FWIW, LGTM:

Reviewed-by: Leonardo Bras <leobras at redhat.com>


Just a suggestion: In this patch I could see a lot of usage changes to
arch_spinlock_t, and only at the end I could see the actual change in the .h
file.

In cases like this, it looks nicer to see the .h file first.

I recently found out about this git diff.orderFile option, which helps to
achieve exactly this.

I use the following git.orderfile, adapted from qemu:

############################################################################
#
# order file for git, to produce patches which are easier to review
# by diffing the important stuff like interface changes first.
#
# one-off usage:
#   git diff -O scripts/git.orderfile ...
#
# add to git config:
#   git config diff.orderFile scripts/git.orderfile
#

MAINTAINERS

# Documentation
Documentation/*
*.rst
*.rst.inc

# build system
Kbuild
Makefile*
*.mak

# semantic patches
*.cocci

# headers
*.h
*.h.inc

# code
*.c
*.c.inc